Many portable telecommunications test instruments are used to monitor the status of a telephone line or similar signal line. Such instruments are generally connected to the telephone line and generates tones that are used to test the line. Often, there are crude line status indicators to inform the user that a voltage is present on the line. However, these voltages are often sufficiently high in potential that the voltage will damages the instrument and may even injure the operator.
It will, therefore, be appreciated that there is a significant need for a handheld, battery powered telecommunications instrument that will not be damaged by abnormal voltages that may be present on the line and, furthermore, will indicate the presence of abnormal line conditions.